It is normal in most hospitals today to provide in-room service of a various medical gases such as oxygen, air, nitrous oxide, as well as a source of vacuum for suction equipment. The gases are generally provided under pressure or vacuum from a central source. A user can conveniently plug in the various equipment that utilize the particular service with a specially designed, keyed adapter that is generally connected to medical tubing for delivery to its end use device.
A typical connector assembly for medical gases usually includes a wall outlet having a cylindrical housing in fluid communication with a specified gas source and being fixed in the wall during construction, and a front unit which is a gas specific portion for gases such as oxygen, nitrous oxide and air, defining diameter-indexed two-stage bores.
A primary valve is provided within a tubing of the front unit which is usually in a closed position and can be pressed-open by a plunger of the adapter at the ends of hoses or gas-using devices.
A secondary valve is provided within the cylindrical body installed in the wall, which is pressed in an open position by the tubing of the front unit when the front unit is connected to the wall outlet. The secondary valve returns to a closed position to prevent gas leakage through the wall outlet when the front unit is removed from the wall outlet for services, such as cleaning or repair.
Typical examples of the connector assemblies for medical gases are described in U.S. Pat. No. 3,563,267 which issued to Thompson on Feb. 16, 1971, U.S. Pat. No. 4,190,075, which issued to Kayser on Feb. 26, 1980 and U.S. Pat. No. 5,236,005, which issued to Berg on Aug. 17, 1993.
As technology develops, the connector assemblies for medical gases are improved. New connector assemblies with updated technologies can be conveniently installed during construction of buildings. However, it is not convenient to install new connector assemblies for replacing old ones in renovations of the medical gas systems in hospitals. A wall outlet containing the secondary valve is usually welded to a gas supply pipe, both being buried within the wall. The decorative exterior of the wall, surrounding the wall outlet, has to be demolished and the existing wall outlet has to be cut from the pipe in order to substitute a new connector assembly. After the wall outlet of the new connector assembly is welded to the pipe in the wall, the wall must be mended with new cladding material. It is a costly process.
Therefore, a structure of connector assemblies for medical gases is desirable to enable the connector assemblies to be detachably connected with existing wall outlets in order to avoid the demolition process during renovations of medical gas systems.
Improved connector assemblies for gases which can be conveniently connected to an existing wall outlet of one type is described, for example, in U.S. Pat. No. 4,562,856, which issued to Garvey et al., on Jan. 7, 1986. A major aspect of the device described in this U.S. Patent, is to incorporate the primary valve and the secondary valve into a single cylindrical body which has a threaded front end conforming to D.I.S.S. (Diameter Indexing Safety System) standard and a threaded rear end for threadedly engaging a corresponding threaded connector defined in an existing wall outlet. This ensures that the internal indexing diameters are not removed during servicing because the cylindrical body is to be left affixed to its primary attachment.
The single body structure, however, leads to problems regarding safety issues. A liquid thread locker, Loctite 271, is applied on the threaded rear end of the cylindrical body to lock the threaded connection with the wall outlet after the liquid becomes solid. The thread locker is an inflammable material, especially in an oxygen-rich environment. The high operating pressure, at 50 psi required in an oxygen system in hospitals increases the risks of igniting the material. It is apparent that the device is not suitable for use relating to an oxygen supply system. After a long period of time, the solid material ages and loses its locking function. Frequent engaging and disengaging adapters to and from the threaded front end of the cylindrical body may eventually loosen the threaded connection between the rear end of the cylindrical body and the wall outlet. Therefore, there is a risk of suddenly losing the connection, and the device under the pressure of 50 psi may eject from the wall outlet.
A structure of a connector assembly for medical gases with improvements regarding a large gas flow is also desirable. A pressure drop through the connector assembly is expected not more than 4 psi according to the standard. Most devices in prior art have a pressure drop of about 8 to 12 psi and the device suggested in U.S. Pat. No. 4,562,856 has a pressure drop ranged from 6 to 8 psi.